932 Appendix III.
three Lancashire boilers of 7 ft, 7'.. 6", and 8 ft. diameter
respectively, on the previous premises, we must first find G the
grate surface. Taking all grate width at 6 ft., we have :
For 7 ft. boiler, grates about 6 ft. long, and area = 36 sq. ft.
p. .. _
o v_J C7 vji ii«_)c-»
Similarly for the j'..6" boiler, grates about 6'..6" long'
and area = 39 sq. ft
.-. I H. P. = 8G - 8x39 = 312
And for the 8 ft. boiler, grates about 7 ft. long, and
area = 42 sq. ft.
.-. LH.P. = 8x42 = 336
For other boilers the evaporation would depend upon the
efficiency as compared with the above; and perhaps the steam
used by the engine might be raised to 30 Ibs. wt. per I. H, P. hour.
Si; i jj jP. 674. Acceleration of Engine Piston : Klein's con-
4' '. struction.
\ 4 ' ,*
ft*1 When drawing an acceleration curve to a given velocity
p,j 1 curve two cases present themselves, one where the base line
tlj / represents time, and the other where it shews distance. The
if A construction for the former, p. 860, is easily and correctly met
I! ;*< by graphic differentiation, For a distance base, Proell's method,
i| i\ pp. 492 and 863, is very convenient for general cases, but when
*"' adopted for the harmonic motion of an engine piston, as at
f p. 674, it does not give absolute results at the dead points. We
shall, therefore, here describe the construction due to Prof. Klein
( !'j of America, which, though more cumbersome, and only applicable
\l to the crank and connecting-rod, gives certain aad accurate
1 '# values at all points of the stroke.
Referring to Fig. 886, let AB be the crank and BC the con-
necting-rod. On BC as diameter describe a circle. Producing
c B to i>, describe a second circle having B as centre and B D
as radius, and cutting the frst circle in E and P. Then, EF
will cross AC in G, and GA will be the acceleration of c, which